Green faces in sculpt mode
Here's how I fixed it on my end.

Switch to edit mode and then press 2 for edge selection mode.
Select &gt; All by Trait &gt; Non Manifold
Deselect the open face at the very top of the arm
Press X &gt; Delete Vertices
Select &gt; All by Trait &gt; Non Manifold (Again)
Press F to fill all the remaining holes.
Add a Remesh modifier to the object.
Set Voxel Size to .003 and Adaptivity to 0. Enable smooth shading.
Hit apply on the modifier and continue sculpting without errors. You might need to smooth out some areas after the remesh.

Here are images of these steps: